Detailed notes on carbs Flashcards
(19 cards)
What are carbohydrates?
- Carbs are basically made up of C, H and O (term comes from carbon= C and Hydrates= water)
- Occur primarily in plants
- Found in lactose and glycogen (meat)
- Photosynthesis produces carbs (energy)
Classification of carbohydrates based on?
- Saccharide units
- Saccharide units and health
- Glycemic index
Classification based on saccharide units?
Related to the size of the molecules in simple and complex sugars
Classification based on saccharide units and health?
Shown in the table. they are broadly classified as
- simple carbs: Monosaccharides and disaccharides
- Complex carbs: Starches and dietary fibre
In addition the digestibility is also indicated in the table (see other notes for table)
Glycemic index
Is based on how rapidly the carbs are taken up into the bloodstream. Is an index used to rank foods according to their different behaviour in our bodies - blood glucose levels.
Another definition is:
- A measure of how fast and how far blood sugar raised after you eat a food that contains carbs.
Key factors tat determine the glycemic index of a food?
- Fiber content
- Type of starch
- Physical form
- Ripeness
How fiber effect GI?
- Is the amount of relatively indigestible polysaccharides (cell wall)
- This determines the speed at which digestive enzymes attack the starch carbs and therefore the release of sugar molecules into the bloodstream
How type of starch effect Gi?
Eg. Boiled rwhich rice appears easier to break into sugar molecules than boiled potato
How Physical form of carb effects GI?
Finely ground grains are easier to digest then coarsely ground grains
How ripeness of carb effects GI?
Particularly relates to fruit. Ripe ones are sweeter and have more sugar and higher GI than unripe
Properties of carbs
- Solubility
- Crystallization
- Colligative properties
- Sweetness
- Colour
- Humactancy’hygroscopicity
- Viscosity
carb solubility
Surgars vary in solubility. Decreasing order: - Fructose - Surcose - Glucose - Maltose - Lactose
Crystallisation
The concentration and temp for cooking sugar solutions is determined whether to solution is:
- Unsaturated
- Saturated
- Supersaturated
Unsaturated solution>
Does not contain all the dissolved solute that the solvent can hold.
Eg. 10g of sugar in 100ml of water will give us an unsaturated solution,
Saturated solution?
Contains all the dissolved solute that the solvent can hold at a definite temperature.
Eg. 203.9g of sugar to 100ml water at 20 degrees will give us a saturated solution
Supersaturated solution?
Contains more solute than the solvent can hold @ a particular temp.
Eg. 487.2 g of sugar in 100ml water at 100 degrees is a saturated solution. If the solution in allowed to cool to 20 degrees the solution would have contained more sugar than the water can hold.
Note! this excess beyond saturation remains in solution as the temperature drops until crystallisation is initiated by treatmeants including stirring or adding crystals
Factors effecting crystal growth and size? (saturated)
- Temperature
- rate of cooling
- amount of seeding at the metastable region
- agitation
- purity of raw material
Carb colour
Only carbs that are reducing sugars are able to react with amino groups to form a brown and flavoursome colour.
The reaction forming this brown colour is called “maillard reaction”or carboxyl-amine browning.
This means that for sucrose to participate in the ration between the conbonyl group of reducing guards and the free amino groups of protein, is has to be cleaved (split/cut) at the alpha 1-4 linkage.
This gives us glucose and fructose which are reducing sugars and therefore these can then participate in the Maillard reaction.
Hydrolisis
Hydrolysis is the breakdown of a complex substance to a simple substance by chemical reaction with water molecules. The word “hydro” refers to water and “lysis” refers to breakdown.
Components of food including carbohydrates, proteins and lipids do undergo hydrolysis and these reactions are accelerates by certain factors including acid, heat or enzymes.
